There are many applications in which a firing unit is utilized to initiate or detonate explosive or pyrotechnic materials for actuation or detonation of a device or system. Examples include such things as weapon systems, aerospace systems such as rocket motors, airbag initiators, parachute harness connectors, and other systems. Firing units utilized in weapon systems, aerospace systems, and other systems typically include an electronics assembly and an initiation device. Such explosive or pyrotechnic materials may be ignited in several different ways. Typically, explosive materials have been ignited by flame ignition (e.g., fuzes or ignition of a priming explosive), impact (which often ignites a priming explosive), chemical interaction (e.g., contact with a reactive or activating fluid), or electrical ignition. Electrical ignition may occur in at least two distinct ways: by ignition of a priming material (e.g., electrically ignited blasting cap or priming material) or by direct energizing of an explosive mass by electrical power. A firing unit may include an explosive material secured within a housing, an initiation device configured to ignite the explosive material, and to an electronics assembly electrically connected to the initiation device. The firing unit may be inserted into a system containing ignitable material to be activated or detonated (e.g., rocket fuel, primary explosive, booster charge, or ignitable compositions). When the electronics assembly in the firing unit is activated, the electronics assembly activates the initiation device, which causes ignition of the explosive material.
Generally, the electronics assembly and the initiation device of a firing unit are assembled together such that the initiation device may not be nondestructively removed from the electronic assembly or, in some instances, may be configured such that the initiation device is separable from the electronic assembly. However, the separability of the firing unit may be undesirable in some instances because the ability to remove the electronics assembly from the initiation device may compromise or deteriorate the electronic connections between the firing unit and the initiation device. For example, use of a separable electrical connection between the electronics assembly and the initiation device may increase the inductance of the firing circuit. An increase in the inductance of a firing circuit may be undesirable in such systems employing a high voltage firing unit (HVFU). For example, an initiation device such as an exploding foil initiator (EFI) may require a relatively large amount of voltage and current from the electronics assembly to ignite the EFI. Increasing the inductance of the firing circuit may compromise the ability of the electronics assembly to reliably ignite the EFI, decreasing the reliability and safety of the firing unit.
Furthermore, a separable electrical connection between the electronics assembly and the initiation device may compromise the ability of the firing unit to be sealed from a surrounding environment in certain applications where such a seal is desirable. Finally, a separable electrical connection between the electronics assembly and the initiation device may undesirably increase any, some, or all of size, weight, and cost of the firing unit, which may be especially undesirable where the firing unit is implemented in systems utilized in aerospace flight.